Section 675 IAC 30-8-2 - MAWP for nonstandard boilersAuthority: IC 22-13-2-8
Affected: IC 22-15-6
Sec. 2.
(a) The MAWP for the shell of a nonstandard boiler or drum shall be determined by the strength of the weakest section of the structure, computed from the thickness of the plate, the tensile strength of the plate, the efficiency of the longitudinal joint or tube ligaments, the inside diameter of the outside course, and the factor of safety. The equation shall be: Click here to view Image
Where: P = Maximum allowable working pressure, in psig.
TS = Ultimate tensile strength of shell plates, in psi.
t = Minimum thickness of shell plate, in weakest course, in inches.
E = Efficiency of longitudinal joint or tube hole ligaments, whichever is less. For riveted construction, E shall be determined by the methods illustrated in Section I of the ASME B&PVC (1971 edition). For tube hole ligaments, E shall be determined by the rules in Section I of the ASME B&PVC.
R = One-half (1/2) the inside diameter of the weakest course of shell or drum in inches.
FS = Factor of safety as permitted in subsection (e).
(b) When the tensile strength of steel or wrought iron shell plates is not known, it shall be taken as fifty-five thousand (55,000) psi for steel and forty-five thousand (45,000) psi for wrought iron.(c) The resistance to crushing of mild steel shall be taken as ninety-five thousand (95,000) psi for each square inch of cross-sectional area.(d) When computing the ultimate strength of rivets in shear, the following values in psi of the cross-sectional area of the rivet shank shall be used: | Iron rivets in single shear | 38,000 |
| Iron rivets in double shear | 76,000 |
| Steel rivets in single shear | 44,000 |
| Steel rivets in double shear | 88,000 |
When the diameter of the rivet holes in the longitudinal joints of a boiler is not known, the diameter and cross-sectional area of rivets, after driving, may be selected by cutting out one (1) rivet in the body of the joint and measuring it, or as follows:
SIZES OF RIVETS BASED ON PLATE THICKNESS
1/4" t (11/16" rivet)
9/32" t (11/16" rivet)
5/16" t (3/4" rivet)
11/32" t (3/4" rivet)
3/8" t (13/16" rivet)
13/32" t (13/16" rivet)
7/16" t (15/16" rivet)
15/32" t (15/16" rivet)
1/2" t (15/16" rivet)
9/16" t (17/16" rivet)
5/8" t (17/16" rivet).
Rivet size is based on diameter after driving.
(e) The following factors of safety shall be increased based on an extrapolation of them as a function of the age and condition of the boiler: (1) The lowest factor of safety permissible on existing nonstandard installations shall be four and one-half (41/2) excepting for horizontal return tubular boilers having continuous lap seams more than twelve (12) feet in length where the factor of safety shall be eight (8), provided that, when this latter type of boiler is removed from its existing setting, it shall not be reinstalled for pressures in excess of fifteen (15) psig.(2) Reinstalled or secondhand boilers shall have a minimum factor of safety of six (6) when the longitudinal seams are of lap riveted construction, and a minimum factor of safety of five (5) when the longitudinal seams are of butt and double strap construction.(f) The age limit of a horizontal return tubular, flue, or cylinder boiler having a longitudinal lap joint and operating at a pressure in excess of fifty (50) psig shall be thirty (30) years.Fire Prevention and Building Safety Commission; 675 IAC 30-8-2; filed Jan 5, 1996, 10:15 a.m.: 19 IR 1128; readopted filed Jul 9, 2001, 1:33 p.m.: 24 IR 3822; readopted filed Sep 21, 2007, 9:16 a.m.: 20071010-IR-680070389RFA; readopted filed Oct 19, 2007, 1:08 p.m.: 20071114-IR-680070389RFA; readopted filed Sep 5, 2013, 10:09 a.m.: 20131009-IR-680130182RFA; readopted filed 9/4/2019, 2:20 p.m.: 20191002-IR-675190336RFAFiled 4/28/2021, 11:03 a.m.: 20210526-IR-675200627FRA, eff 7/1/2021Transferred from the Boiler and Pressure Vessel Rules Board ( 680 IAC 2-8-2) to the Fire Prevention and Building Safety Commission ( 675 IAC 30-8-2) by P.L. 249-2019, SECTION 15, effective July 1, 2019.